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Health Benefits of Seaweed

In this Article

In this Article
In this Article
  • Health Benefits
  • Nutrition
  • How to Use Seaweed

Seaweed is a general term that refers to a number of algae and marine plants that grow along rocky shorelines around the world. There are many different types, including red (Rhodophyta), green (Chlorophyta), blue-green, and brown (Phaeophyceae). Some of the most common types of edible seaweeds include:

  • Wakame
  • Dulse
  • Kombu
  • Kelp
  • Sea lettuce
  • Nori
  • Arame
  • Chlorella

While seaweeds grow in all different areas of the world, they’re most prevalent in Asian cuisines, where they’re featured in sushi, salads, soups, and stews.

In prehistoric times, seaweed was an important part of coastal peoples’ diets. Today, more than 145 varieties are used around the world.

While it doesn’t have the same popularity in the United States as it does in Asian countries, people are beginning to recognize that seaweed is a nutritious addition to the diet and provides several health benefits.

Health Benefits

Seaweed is an excellent source of iodine, a vital trace mineral that plays a critical role in thyroid health. The body doesn’t make iodine on its own, so you need to get it from food sources or supplements.В

Health benefits of seaweed include:

Improves thyroid function.

Your thyroid plays a crucial role in your overall health, and iodine plays a vital role in its ability to function properly. Insufficient iodine means that your thyroid can’t make enough thyroid hormone (a condition known as hypothyroidism), which regulates many bodily functions, including metabolism. If you don’t get enough iodine, you may develop a goiter, a visible enlargement of your thyroid. Iodine deficiency can also impact children during development, both in the womb and during early childhood.

May improve gut health.

Seaweed has carrageenans, agars, fucoidans, which act as prebiotics, non-digestible fibers that feed the healthy bacteria in your digestive tract. Sulfated polysaccharides (sugars found in seaweed) help to increase the growth of the good bacteria and increase the short-term fatty acids that keep the lining of your gut healthy.

Improves heart health.

Some studies show that seaweed intake may help to reduce blood pressure. It may also help to reduce LDL cholesterol and total cholesterol levels. Results of human studies are promising, but more research is needed.В

Continued

Stabilizes blood sugar levels.

Brown seaweed contains fucoxanthin, an antioxidant that gives the vegetable its color. The antioxidant may play a role in helping to improve blood sugar control and reducing your risk of developing type 2 diabetes.

May boost your immune health. Some studies show that seaweed may help to boost your immune system by fighting viruses and preventing them from getting into your system. More studies are needed, however.В

May reduce cancer risk. Adding seaweed to your diet may help to reduce your risk of developing certain types of cancer. It may decrease estrogen levels, which may reduce the risk of breast cancer. Again, there are very few human studies available, so more research is necessary. В

Nutrition

While the nutrition content of seaweed varies based on where it grows and what type it is, they all contain a healthy vitamin and mineral profile. Most seaweeds contain nutrients such as:

  • Vitamin A
  • Vitamin B1
  • Vitamin B2
  • Vitamin C
  • Vitamin E
  • Vitamin K
  • Calcium
  • Folate
  • Potassium
  • Iron
  • Manganese
  • Copper

Seaweed contains many antioxidants in the form of certain vitamins (A, C, and E) and protective pigments. It has a decent amount of iodine, a trace mineral vital for the health and function of the thyroid. Some seaweeds, such as purple laver, contain a good amount of B12 as well.

Nutrients Per Serving

A 2-tablespoon serving of wakame seaweed has:

  • Calories: 5
  • Protein: 0 grams
  • Fat: 0 grams
  • Carbohydrates: 1 gram
  • Fiber: 0 grams
  • Sugar: 0 grams

Things to Watch Out For

Eating fresh seaweed is generally considered safe for most people. While the plant offers many health benefits, there are a few things to watch out for:

Too much iodine. While iodine is a vital trace mineral for thyroid health, too much can have the opposite effect.В

May interfere with certain medications. Seaweed contains a high amount of potassium, which can be harmful to individuals with kidney disease. Seaweed also contains vitamin K, which could interfere with blood-thinning medications such as Warfarin.В

Some varieties may have high levels of heavy metals. Some varieties of seaweed may contain high levels of arsenic, cadmium, mercury, or lead, depending upon how they’re grown. The FDA regulates the heavy metals in fresh seaweed, but not supplements.В

Continued

How to Use Seaweed

Many grocery stores carry some forms of dried seaweed. You may find dried seaweed snacks, nori for sushi, or dried dulse flakes. Many Asian food stores carry a greater variety of dried and fresh seaweed products.В

There are many ways to add seaweed into your diet, including:

  • Make a soup broth dried kelp or kombu
  • Mix fresh arame and wakame with vinegar, sesame oil, scallions, and garlic for a seaweed salad
  • Top meals with a mix of ground nori, kombu, dulse, salt, black pepper, and sesame seeds
  • Snack on dried nori
  • Add kombu to cooked beans
  • Make homemade sushi
  • Make a vegan “tuna” salad with chickpeas, vegan mayonnaise, celery, red onion, salt, pepper, and dulse flakes
Sources

BBC News: “Seaweed: Should People Eat More of It?”

University of Michigan-Michigan Medicine: “Thyroid Hormone Production and Function.”

Sultan Qaboos University Medical Journal: “Health Consequences of Iodine Deficiency.”

Marine Drugs: “Prebiotics from Marine Macroalgae for Human and Animal Health Applications.”

International Journal of Biological Macromolecules: “Digestibility of Sulfated Polysaccharide from the Brown Seaweed Ascophyllum nodosum and Its Effect on the Human Gut Microbiota In Vitro.”

Journal of Clinical Biochemistry and Nutrition: “Clinical Effects of Brown Seaweed, Undaria pinnatifida (Wakame), on Blood Pressure in Hypertensive Subjects.”

Journal of Nutritional Science: “Reduction of HbA1c Levels by Fucoxanthin-Enriched Akamoku Oil Possibly Involves the Thrifty Allele of Uncoupling Protein 1 (UCP1): A Randomized Controlled Trial in Normal-Weight and Obese Japanese Adults.”Current Medicinal Chemistry: “Phenolic Compounds from Edible Algae: Bioactivity and Health Benefits.”

PloS One: “Aqueous Extracts of Marine Brown Alga Lobophora variegate Inhibit HIV-1 Infection at the Level of Virus Entry into Cells.”

Journal of Applied Phycology: “The Consumption of Seaweed as a Protective Factor in the Etiology of Breast Cancer: Proof of Principle.”

Nutrition Reviews: “Nutritional Value of Edible Seaweeds.”

Nutrients: “Vitamin B12-Containing Plant Food Sources for Vegetarians.”

ESHA Research, Inc., Salem, Oregon.

Endocrine Journal: “Suppression of Thyroid Function During Ingestion of Seaweed “Kombu” (Laminaria japonoca) in Normal Japanese Adults.”

Journal of Medical Case Reports: “Palmaria pamata (Dulse) as an Unusual Maritime Aeteology of Hyperkalemia in a Patient with Chronic Renal Failure: A Case Report.”

Learn about the health benefits of seaweed, its nutrients, and how it can help improve thyroid health and function, reduce your risk of cancer, boost your immune system, and more.

Seaweed Nutrition Facts and Health Benefits

Mark Stibich, PhD, FIDSA, is a behavior change expert with experience helping individuals make lasting lifestyle improvements.

Mia Syn, MS, RDN is a registered dietitian nutritionist with a master of science in human nutrition. She is also the host of Good Food Friday on ABC News 4.

Verywell / Alexandra Shytsman

Seaweed has been popular in Asian cuisine for centuries, and it’s starting to catch on in the West as well. Although seaweed offers several promising health benefits, it also carries potential pollutants from the ocean to your plate. If you’ve heard mixed advice on the pros and cons of eating seaweed, here’s some information to help clarify the facts.

Seaweed Nutrition Facts

The following nutrition information is provided by the USDA for 1 cup (80g) of raw wakame seaweed.  

  • Calories: 36
  • Fat: 0.5g
  • Sodium: 698mg
  • Carbohydrates: 7.3g
  • Fiber: 0.4g
  • Sugars: 0.5g
  • Protein: 2.4g

Carbs

There are a little over 7 grams of carbohydrate in 1 cup of raw seaweed. Of this, less than 1 gram comes from fiber and sugar combined. Seaweed contains various polysaccharides that act as antioxidants, providing numerous health benefits.  

Raw seaweed is very low in fat with a 1/2 gram per cup.

Protein

A 1-cup serving of raw seaweed provides 2.4 grams of protein.

Vitamins and Minerals

Seaweed is rich in several vitamins and minerals including calcium, potassium, vitamin C, folate, beta carotene, and vitamin K. The sodium content of seaweed varies based on the brand and preparation method but can be up to 698 milligrams per cup (raw). Some species of edible seaweeds also provide vitamin D and B12, two essential nutrients that can be hard to come by in plant foods.   Seaweed is also a good source of iodine.

In addition to vitamins and minerals, seaweed provides unique plant compounds that have been linked to promoting good health and disease prevention.

May Protect Against Asthma

Data reviewing the 2013–2016 Korea National Health and Nutrition Examination Survey (KNHANES) discovered that lower intakes of seaweed and seafood were associated with higher rates of asthma.   Because asthma is an inflammatory disease, it’s hypothesized that the polyunsaturated fats and vitamins found in these foods are protective. Although more research is needed to confirm a cause and effect benefit, introducing seaweed during pregnancy and early childhood appears to be beneficial.

Reduces Risk of Osteoporosis

Oxidation from free radicals is associated with a host of health issues, including the weakening of bones. Seaweed contains antioxidant compounds, called fucoidans, which are shown to prevent bone breakdown by free radicals.   Specifically, fucoidans protect osteoblasts (the cells responsible for building bone) against apotosis, or cell death, that may otherwise be induced by oxidative stress. Seaweed also provides vitamin K and calcium, two key nutrients for bone strength.

May Aid Cancer Prevention

The fucoidans in seaweed have also been studied for cancer prevention. While human clinical trials are limited, fucoidan’s ability to influence programmed cell death shows promise as a potential supplement to traditional cancer treatments.   Like other vegetables, seaweed is also a source of antioxidants (like vitamin C and beta carotene). These compounds are known for cancer prevention qualities, especially when consumed as part of a nutrient-dense eating plan (rather than just supplementation).

Promotes Heart Health

Seaweed is a good source of soluble fiber, especially dulse seaweed and kombu which provide 5 to 6 grams per serving.   Soluble fiber binds to cholesterol, pulling it out of the body through waste. In addition to reducing cholesterol, seaweed can also help lower blood pressure levels due to its potassium content (just watch out for added sodium). Finally, the folate in seaweed keeps homocysteine levels down (a sign of inflammation), reducing the risk of stroke.  

Supports Weight Loss

The main form of soluble fiber found in seaweed is alginate. Studies show that alginate improves satiety by delaying gastric emptying, which can lead to a reduction in subsequent food intake.  

Additionally, seaweed contains protein, which is also known to produce feelings of fullness. Seaweed offers ample nutrients and flavor for a minimal number of calories. Seaweed wraps, soups, or salads can be a good choice to help keep hunger pangs at bay while trying to lose weight.

Allergies

Allergies exclusively to seaweed are not commonly reported, but they are possible. Shellfish allergies and iodine allergies more likely to occur. Shellfish allergies can be very dangerous so using caution around any possible source of cross-contamination (including seaweed) may be advised. If someone is allergic to iodine, the natural iodine content of seaweed would be a trigger.   Speak to an allergist if you suspect that you have a seaweed allergy.

Adverse Effects

As a natural source of vitamin K, seaweed may interfere with the anticoagulant effects of blood thinners like Coumadin (warfarin). Maintaining a consistent intake of foods that are high in vitamin K will help your doctor determine the correct dosage of medication for you.  

Depending on where seaweed is sourced, it may contain high levels of heavy metals like mercury and arsenic. Varying the types of seaweed you eat, avoiding hijiki seaweed (which is known to be high in arsenic), and limiting your intake to three times per week can help you reduce heavy metal exposure from seaweed.   Many U.S.-based companies test for heavy metals so check on the label for testing.

Varieties

There are many different color variations of edible seaweed that come from different species. Nori, or purple laver, is a dark-colored seaweed used to wrap sushi. This is one of the most nutritious types of seaweed with a high protein and nutrient content.  

Aonori, or green laver, is cultivated in Japan and sometimes referred to as “sea lettuce.” Kombu (in Japan) and haidai (in China) is another type of dried seaweed. A type of red algae with leathery fronds is called Dulse. Dulse is commonly chewed as a raw snack in Ireland or cooked with potatoes. Other edible variations of seaweed include winged kelp, Irish moss, sea grapes, mozuku, and hiziki.

When It’s Best

Seaweed can be eaten raw or dried, depending on the variety. You may be able to find more popular varieties, like nori, in your local supermarket, but other types of seaweed can be harder to come by. Asian grocery stores are likely to offer a fuller selection.

Storage and Food Safety

Fresh seaweed should be handled the same way other leafy greens are handled. Wash fresh seaweed under running water before consuming or preparing. Store fresh seaweed in the refrigerator.

Dried seaweed should be placed in an airtight container after opening. Follow the expiration dates listed on the package for maximum freshness. Looking for a reputable food company online or at the grocery store will help you avoid heavy metals and other toxins.  

How to Prepare

The easiest way to eat seaweed is by using dried seaweed wrapper (nori), the kind you find in sushi restaurants. Use it to wrap almost anything. You can also break into pieces and sprinkle dried seaweed flakes onto a salad or other dishes for a nutritional boost. Seaweed is also popular in Asian soups, such as miso soup.

Seaweed is a nutritious protein source with minimal calories. A cup of cooked seaweed provides over 5.5 grams of protein and lots of vitamins.